This project utilizes single neuron recording and operant conditioning techniques in behaving monkeys to study brain mechanisms underlying voluntary movement. Monkeys are trained to make precise movements of a handle whose position controls a visual display, and stimuli are delivered via the handle by means of an electronically controlled torque motor in order to determine how sensory feedback is processed. Recordings from primary sensory cortex when movements are triggered by a vibrotactile stimulus show that central influences corollary with initiation of an active movement modify sensory cortex information processing. In a separate experiment on basal ganglia it has been found that there is a class of neurons exhibiting responsiveness when a stiumlus serves as a cue for movement but not when the motor response to this same cue has been extinguished. Taken together, these studies provide new evidence for brain loci involved in control of voluntary movement.